Fuel injectors are commonly employed in internal combustion engines to provide precise metering of fuel for injection into each combustion chamber. An electro-magnetic fuel injector typically utilizes an electromagnetic solenoid assembly to supply an actuating force to a fuel metering valve. Typically, the fuel metering valve is a plunger style needle valve which reciprocates between a closed position, where the needle is seated in a valve seat to prevent fuel from escaping through a metering orifice into the combustion chamber, and an open position, where the needle is lifted from the valve seat, allowing fuel to discharge through the metering orifice for injection into the combustion chamber.
The fuel injector atomizes the fuel during injection into the combustion chamber, breaking the fuel into a large number of very small particles, increasing the surface area of the fuel being injected, and allowing the oxidizer, typically ambient air, to more thoroughly mix with the fuel prior to combustion. The precise metering and atomization of the fuel reduces combustion emissions and increases the fuel efficiency of the engine.
Additionally, pressurized assist air can be injected into the fuel to assist in the atomization of the fuel into small particles. To optimize the fuel break-up, it would be beneficial to provide the pressurized air generally along the same direction as the fuel flow in order to reduce fuel pressure loss due to the air impacting the fuel. To do this, the air can be provided through a hollow needle. However, due to clearances between parts, fuel can leak into the needle, impeding the air flow.
It would be beneficial to provide a fuel injector in which both fuel and assist air is provided simultaneously by the operation of the fuel injector, and in which fuel cannot leak into the supply of assist air.